1. Field of the Invention
This invention relates to photography and, more particularly, to a pivoting exposure control system for photographic apparatus.
2. Description of the Prior Art
Thin and compact photographic cameras of the reflex type have been developed wherein the exposure of the film unit is electronically controlled and the film unit may be rapidly processed at a processing station within the photographic camera. A version of such a camera having a compactness and thinness suited to permit convenient carrying in the pocket of a garment is described in a U.S. Patent entitled Reflex Camera by E. H. Land, U.S. Pat. No. 3,672,281. Such cameras are of the single lens reflex variety and require a complex exposure control system in order to accommodate a requisite viewing and focusing mode during which time the single lens reflex camera is in a normally open status to unblock the passage of light through the exposure opening to a viewfinder. At the commencement of an exposure cycle, the shutter mechanism of the camera exposure control system is driven into a closed or light blocking orientation whereupon the photographic camera is automatically operated to change from the viewing and focusing mode to an exposure mode in which photosensitive film is made accessible to the optical path of the taking lens of the camera. When the camera has assumed the exposure mode of operation, the exposure control system operates to release a shutter mechanism from its light blocking orientation wherein such exposure control parameters as exposure interval and aperture size are controlled as a function of scene brightness as evaluated with respect to the sensitometric characteristics of the film being exposed. At the termination of the electronically determined exposure interval, the shutter is again driven to a fully closed or light blocking position to terminate exposure until such time as the camera reassumes the viewing or focusing mode.
The exposure mechanisms for such photographic cameras generally include two cooperately moving shutter blades which ride transversely within supporting tracks. The blades are formed with selectively shaped aperture openings which, depending upon the position of the blades, symmetrically overlap over a light entering exposure opening within the camera housing. Such blades may be connected to define a progression of apertures over the light entering opening in the camera as a result of their connection with a so-called "walking beam" or actuator which is rotatively mounted with respect to the camera housing. Elongate slots are generally formed in the outward tip portions of the beam for the purpose of providing connections with pins extending respectively from the blades. Thus interconnected, the blades will move simultaneously and in correspondence with each other to define a symmetrically configured and variable aperture opening over the camera light entering opening.
Single reflex photographic cameras embodying the above-described exposure control system are suitable for use with film units described in detail in U.S. Patent to E. H. Land, U.S. Pat. No. 3,415,644 entitled Novel Photographic Products and Processes. Such film units include all the materials necessary to produce a positive photographic print by an image forming process which is now well known in the art and involves the formation of transverse image forming substances in an exposed photosensitive element by their diffusion in a manner forming a visual positive image.
Shutter blade mechanisms of the above-described type, although satisfactory for their intended purpose, have proven costly due to the use of supporting tracks which must be precisely dimensioned. In addition, the use of a supporting track to slidably engage a blade element along a substantial portion of the length thereof, may require the use of a high actuating force to overcome the mechanical friction between the blade and track.
Therefore, it is a primary object for this invention to provide a simple and economical exposure control system for a photographic camera which utilizes film units of the type having all materials included therein necessary to produce a positive photographic print.
It is also an object of this invention to provide a simple and economical exposure control system for a photographic camera of the reflex type capable of utilizing film units of the type described in detail in U.S. Pat. No. 3,415,646 supra.
It is a further object of this invention to provide an exposure control system for a photographic camera wherein the exposure control system includes a simple and economical shutter blade mechanism for varying both exposure interval and aperture size.
It is an even further object of this invention to provide an exposure control system for a camera of either the reflex or non-reflex type wherein the exposure control system includes a shutter mechanism which functions in a reliable manner without the use of tracked elements to slidably retain a pair of shutter blades.
It is also an object of this invention to provide an exposure control system for a photographic camera wherein the exposure control system includes a shutter mechanism having low coefficients of friction such that the percentage of the overall actuating force devoted to overcoming mechanical friction is substantially reduced in comparison with conventional systems.